Block of inward rectifying K+ channels (KIR) inhibits bradykinin-induced vasodilatation in human forearm resistance vasculature

Objective - To investigate the possible involvement of inward rectifying K+ channels (K-IR) in the response of human resistance vessels to bradykinin in vivo. Methods and Results - Drugs were administered via the brachial artery in healthy male volunteers and forearm blood flow was measured by venous occlusion plethysmography. Inhibition of K-IR by barium chloride (4 mumol min(-1)) alone or with additional inhibition of Na+/ K+ ATPase (ouabain 2.7 mumol min(-1)) reduced responses to bradykinin (30 pmol min(-1)), by 26 +/- 8.3% and 36 +/- 7.2%, respectively ( each P < 0 0.05). Barium with ouabain plus inhibitors of prostaglandin ( PG) and nitric oxide synthesis inhibited but did not abolish responses to bradykinin ( 51 +/- 2.8% inhibition; P < 0.01); norepinephrine (240 pmol min(-1)) caused similar reduction of baseline blood flow, as did this combination of inhibitors, but did not significantly inhibit the response to bradykinin. Barium plus ouabain did not significantly reduce responses to acetylcholine or albuterol. Conclusion - A component of the vasodilator response to bradykinin in human forearm vasculature is mediated by K-IR.